I thought I'd chime in here as I realized this week that I've shipped something like 100 knives now, almost everyone of them Khukuris, that have run from 14 to 30 inches in overall length, running from 15 to 75 ounces.
I don't have much to add to the great comments in the thread, but insofar as packing this style of knife, death to someone shipping a khukuri is putting the knife in a position to have the pommel impacted. If it is, the top dead center postion of the handle that lies under your palm at the pommel swell will almost certainly break off.
The other weak point on the khukuri is the chape, the sharp brass point at the end of the leather-bound wood scabbard, which can be bent or poke through the packaging.
So, starting with a priority mail triangular box, I shove a ball of heavy wrapping paper down into the bottom of the box. Wrap the handle with bubble wrap and tape, folding all of the excess over the pommel and taping that down. Then I do the same thing to the chape, or fold a square of cardboard down over it, securing that sharp tip. If you don't it can end up clean through the box.
Then I wrap bubble wrap or styrofoam wrap over the entire scabbard and secure it and the bubble wrapped handle together with more tape, then the whole thing goes in the box pushed down on the ball of wrapping paper. You don't want the knife to come out of the scabbard if you tug on the handle, so it should be all one wrapped unit. Then fill the top interior section of the box with paper, bubble wrap, or whatever you have, then secure the top flap of the box, taping both ends down.
I bought several excellent knives from Tora years ago, shipped via the Royal Mail, and basically the knives were laid loose inside a cardboard frame that allowed 4" of movement on each end of the knife. By the time I got two of them sections of the buffalo horn were powder, so movement is the enemy.
In some cases because of the thickness of the scabbard at the point where the karda and chakmak rest, or if you are shipping two or more knives in the same box, you have to ship the knife out of the scabbard. In that case I do the same thing, but make a "V" out of a long strip of cardboard and tape it all along the edge and blade tip, then bubble wrap or styrofoam wrap the whole blade and tie that in to the wrapped handle.
The bottom line is that no matter how you do it, the idea is to eliminate any back and forth movement of the knife. No movement means zero possiblity either end of the heavy khukuri will be impacted, which can bend the chape, bend the pommel which will damage the handle, or even split the wood scabbard if hit hard enough.
One final note: IF you ship two knives together in a long box, you essentially have weight at each end and an unsupported area in the middle of the box. In some cases the priority mail box can start to bend in the middle, and tear apart. To prevent that put a double layer of heavy strapping tape in the center of the box to reinforce it. You can often get more weight into these boxes than they can comfortably support, so this helps in that situation.
Norm